Sonic system for deformation of sheet material

ABSTRACT

A system and process for the bending and drawing of metals using vibratory-mechanical energy to facilitate the deformation process. A forming tool or punch is &#39;&#39;&#39;&#39;impact coupled&#39;&#39;&#39;&#39; with the free or unattached end of the transmission line of a piezoelectric electromechanical transducer-transmission line assembly. A mating die is positioned opposite the punch and the metalwork material is inserted therebetween. Intermittent impacts made by the forming tool against the metal blank effectively transfer dynamic force and static force sufficient to perform the desired deformation.

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Susanna ll eihv. 222, 11972 MEWIIC @EISTEM 1Fllt DEWDRMATMBN @11 SHEET! MA'lllElltllAlL inventors: llllildegurrl 1V1. Mtnchenlro, lteynoldsburg; llyttun A. Kendall, .llru, Columbus, both of Ohio The @hio State University, Columbus, Ohio Filed: Aug. 113, 11969 Appl.No.: M91523 Assignee:

US. Cl 72/56, 72/60, 72/347 lint. Cl. ..lll21ldl 26/02, 821d 22/00 Field 01 Ewenrch ..72/'50, 347 56 References Cited UNITED STATES PATENTS 8/1965 Balamuth et a1 ..72/56 3,233,012 12/1966 Bodine, .lr ..72/56 3,341,935 9/1967 Balamuth ..29/470 3,354,688 11/1967 Bodine, Jr ..72/297 Primary Examiner-Richard J. l-lerbst Assistant ExaminerMichael .1. Keenan Attarney-Anthony D. Cennamo [57] ABSTRACT A System and process for the bending and drawing of metals using vibratory-mechanical energy to facilitate the deformation process. A forming tool or punch is impact coupled" with the free or unattached end of the transmission line of a piezoelectric electromechanical transclu.certransmission line assembly. A mating die is positioned opposite the punch and the metalworlc material is inserted therebetween. intermittent impacts made by the forming tool against the metal blank effectively transfer dynamic force and static force sufficient to perform the desired deformation.

'7 Claims, 6 Drawing Figures PATENTEUFEBZE I972 SHEET 1. [IF 2 IN VHN'IY )R. HILDEGARD M. MINCHENKO LYTTON A. KENDALL, JR.

FIG. IO

ATTORNEY PAIENIEUFEB 22 I972 SHEET E OF 2 FIG. 2

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FIG. 3Q

ATTORNEY SONIC SYSTEM FOR BEFORMATHON Oil SHEET MATERTAL CROSS-REFERENCES There is disclosed in US. Pat. No. 3,396,285, for Electromechanical Transducer, by Hildegard M. Minchenko, a transducer capable of delivering extremely high power, i.e., measurable in horsepower (or kilowatts) at an acoustical frequency range. The principle underlying the high-power output is in the structural arrangement of the components immediately associated with the piezoelectric driving elements. In theory and practice, the piezoelectric elements are under radial and axial pressure that assure that they do not operate in tension even under intense sonic action. Significantly, the structural design of this transducer, that permits the extraordinary power output from the driving elements, resides in the novel method of clamping the piezoelectric elements both radially and longitudinally (axially). in this way the acoustic stresses in the piezoelectric elements are always compressive, never tensile, even under maximum voltage excitation.

The transducer disclosed in the aforementioned patent is intended, and therefore utilized, to deliver a steady-state vibratory power output signal. That is, the piezoelectric assembly is a component of a resonant structure that will produce a mechanical vibratory output at the frequency of the driving electrical signal and vice versa. For maximum output the transducer is excited electrically at its mechanical resonant frequency.

There is disclosed in the copending patent application for Sonic Transducer Assembly, Ser. No. 713,031, filed Mar. 14, 1968, now continuation application Ser. No. 14,777, filed Feb. 27, 1970 by Robert C. McMaster, Charles C. Libby, and Keith Likins, and assigned to the Ohio State University, an improved enclosure design for a sonic or ultrasonic transducer. More specifically, the enclosure design is for a resonant structure type of sonic transducer that completely encloses the transducer but yet does not affect the electrical or mechanical characteristics thereof. The enclosure covers the entire structure and even though it is clamped to the structure of the transducer the enclosure permits the nonrestrictive movement of the transducer tip. The enclosure follows the outside contour of the transducer and is fixedly clamped to the transducer at its node (point of minimum amplitude). The top portion of the enclosure is closed, whereas the bottom of the enclosure has an opening to permit vibration of the transducer horn without contact with the housing.

In copending patent application, Ser. No. 605,284, filed Dec. 28, 1966, now US. Pat. No. 3,475,628, for Sonic Transducer Apparatus, by Robert C. McMaster, Charles C. Libby and llildegard M. Minchenko, and assigned to the Ohio State University, there is disclosed an apparatus wherein an impact coupling means is used as an intermediate mechanical member for transmitting the vibratory-mechanical energy from one transducer to another.

Further, it has been disclosed in copending patent application, Ser. No. 713,034, filed Mar. 14, 1968, for Power Conversion Means, by Robert C. McMaster and assigned to the Ohio State University, an intermediate mechanical member for so transmitting the vibratory-mechanical energy positioned by a diaphragm spaced between the two opposing transducers of the system.

There is further disclosed in copending patent application, Ser. No. 819,886, filed Apr. 28, 1969, for intermediary lm pact Device," by Charles C. Libby and William J. White, and assigned to the Ohio State University, a device for effectively delivering vibratory-mechanical energy from the tip of the horn of an electromechanical transducer to a work surface. As disclosed in the last-mentioned application an intermediary impact device is positioned against the tip of the electromechanical transducer. The vibratory-mechanical energy of said transducer is concentrated at the tip of said transducer causing the tip to extend and contract in the axial direction. The transducer tip impacts the intermediary impact device and drives said intermediary impact device against the surface of the material to be formed. The movement of the intermediary impact device is constrained to movement collinear with the axial direction of movement of the transducer tip by means of a dual diaphragm made either of metal or an organic material.

The transducer tip impacts against the intermediary impact device driving said intermediary impact. device away from the transducer tip. The dynamic energy of said intermediary impact device moving away from the transducer tip is absorbed upon impact with the work surface. After the dynamic energy is substantially absorbed, the intermediary impact device recoils causing the intermediary impact device to return to the transducer tip where the device is impacted again by the trans ducer tip. The dual diaphragm constrains the motion of the intermediary impact device to travel in a direction collinear with the axial movement of the transducer tip.

Copending patent application, Ser. No. 637,306, filed May 9, 1967, now continuation application Ser. No. 1,957, filed Mar. 4, 1970 for Sonic Transmission Line, by Charles C. Libby and liarl F. Graff, and assigned to the Ohio State University, discloses apparatus for the delivery of high-power sonic energy from a sonic transducer to a work surface. Such a transmission line is utilized in the present invention.

There is further disclosed in copending patent application, Ser. No. 713,036, filed Mar. 14, 19618, new US. Pat. No. 3,550,417 for Process for the Cold Forming of Metals, by Robert C. McMaster and assigned to the same assignee, a system utilizing sonic energy to facilitate the rolling deformation of metals. This system contemplates the introduction of vibratory-mechanical energy into the work material. The vibratory energy so introduced travels through the work material in wave form. Dynamic stresses created within the work material are additive to those stresses created by externally applied loads. Hence, the work material can be deformed by static forces much lower than those required in conventional metal forming processes.

BACKGROUND Sonic and ultrasonic metal deformation systems disclosed in the prior art have, in general, not effectively assisted metal deformation. in the prior art system the sonic energy is introduced into a rigidly connected working tool. it has now been found that high levels of sonic power could not be introduced into work materials through the tool due to the vibration lifting the tool or forming element out of contact with the work material. The only alternative is to apply very high static forces (exceeding the magnitude of the vibratory force). Further, it has also been found that the resonant frequency of the transducer shifts with contact to a rigid surface. l-lence, since the power supply is tuned a shift in frequen cy of the transducer results in an almost total loss of power.

OBJECTS The principal object of the present invention is to provide a system for the cold drawing and cold bending of metals, alloys, and other materials possessing a stress-strain curve with an elastic region followed by a region of plastic deformation.

Another object of the invention is to provide a method for cold forming whereby the forming operation may be completed in one continuous operation thereby eliminating the need for annealing.

Another object of the invention is to provide a method for working materials not normally considered cold formable.

Still another object of the invention is to provide a method whereby a material can be formed using much lower static loading than those required to perform the same operation using conventional equipment and techniques.

Other objects and features of the present invention will become apparent from a reading of the following detailed description when taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustration of the transducer-transmission line assembly positioned in conjunction with a die and punch to perform a metal deformation operation;

FIG. la is a cross section of the punch and die shown in FIG.

FIG. 2 is an illustration of a deep drawn hemispherical cup drawn from a sheet metal blank using the apparatus illustrated in FIG. 1;

FIG. 2a is an illustration of the punch and die used to form the hemispherical cup illustrated in FIG. 2;

FIG. 3 'is an illustration of a U" bend drawn from a sheet metal blank using the apparatus illustrated in FIG. l; and,

FIG. 3a is an illustration of the punch and die used to form the U bend illustrated inFlG. 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Materials having a stress-strain curve with a region of plastic deformation are permanently deformed when such material is stressed beyond its elastic limit into the region of plastic deformation. Stress is usually defined as an internal reaction of a material to an externally applied force. Where vibratory energy is introduced into the material to be deformed dynamic stresses are established in the material. The dynamic stresses are an internal reaction to the vibratory-mechanical energy introduced into the work material. These dynamic stresses are additive to the conventional static stresses introduced into the material by an externally applied force. Hence, where a material is subjected to vibratory energy, such material can be permanently deformed with static stresses (created by externally applied forces) of much lower magnitude than when such material is not excited with vibratory energy. The dynamic stresses cause essentially all the deformation and the low static stresses serve as control signals which causes the deformation to occur in the desired directions.

The system and method of the present invention contemplates the introduction of vibratory-mechanical energy into sheet metals and alloys to facilitate deep drawing and bending of such materials. Deep drawing is the formation of cup shaped articles or shells by using a punch to force sheet metal into a die. Bending, as performed by the present invention contemplates forcing sheet metal into a die with a punch in a manner analogous to the deep drawing operation.

Deformation in bending is substantially unidirectional; that is, in bending the material tends to elongate or deform primarily in the direction perpendicular to the axis through the radius of the bend. Deformation in deep drawing is omnidirection; that is, the material stretches or deforms in all directions. Bending or deep drawing is carried out using the present invention by using an appropriate die and punch.

Referring now generally to FIG. 1 there is shown an electromechanical piezoelectric transducer 1 supported at its node 8; a vibratory-mechanical energy transmission line 2 securely affixed to the transducer 1; a punch 7 fitted into a punch guide 4; an anvil or die 5 positioned adjacent to, secured to, and aligned with the punch guide 4; and work material 6 positioned between the punch guide 4 and die 5.

The transducer 1 is excited electrically by an alternating polarity input-voltage at the transducers 1 mechanical resonant frequency. This produces a vibratory-mechanical displacement at the tip of the concentrating horn of the transducer l. The vibratory-mechanical energy so produced is transmitted through the transmission line 2 to the vibratorymechanical energy impact coupling device, the punch 7. The punch 7 so excited with vibratory-mechanical energy in turn excites the work material with such energy thereby creating dynamic stresses within the work material 6. The combination of the dynamic stress and static stress (which is induced in the work material 6 by an externally applied static force) causes the work material to deform and conform to the configuration of the die 5 cavity. No springback of the work material 6 so formed occurs.

More specifically, the forming operation is carried out by intermittent impacts made by the punch 7 against the work material 6. By using the impact coupling means the transducer 1 runs freely at its resonant frequency. This makes it possible to use a fixed frequency electric generator for the alternating polarity input-voltage source required to excite the transducer 1 at its mechanical resonant frequency to create vibratorymechanical energy.

FIG. la illustrates an alignment means 3 used in the present invention. The alignment means facilitates the alignment of the transmission line 2 and the punch 7. The alignment means 3 is a cylindrical piece of steel or other suitable material. The alignment means 3 is retained by apertures 9, 10, in the transmission line 2 and punch 7, respectively. The alignment means is disclosed and described in the aforemention copending patent application Ser. No. 605,284, filed Dec. 28, 1966, now U.S. Pat. No. 3,475,628, for Sonic Transducer Apparatus, by Robert C. McMaster, Charles C. Libby, and Hildegard M. Minchenko, and assigned to the Ohio State University. The vibratory-mechanical energy manifested by axial movement at the apertured end of the transmission line 2 intermittently drives the punch 7 against the work material 6 causing the work material 6 to deform and conform to the shape of the cavity of the die 5.

Vibratory-mechanical energy from the transmission line 2 introduced into the punch 7 is transmitted from the punch to the work material 6 when the punch 7 contacts the work material 6. The vibratory-mechanical energy so introduced creates the dynamic stresses in the work material 6. Since the dynamic stresses are additive to static stresses in the work material 6 a low static force F intermittently applied at the transducer 1 node 8 is transmitted to the transducer-transmission line assembly 1, 2, and facilitates the deformation process.

With the application of the static force F to the transducer 1 node 8 the punch 7 (excited with vibratory-mechanical energy) becomes intermittently trapped between the transmission line 2 and the work material 6. During the brief periods of time during which the impact coupling means 3 is so trapped, the static force applied to the transducer 1 node 8 is transmitted through the transmission line 2 and punch 7 to the work material 6. The static force F so applied and transmitted creates static stresses within the work material 6 which combine with the dynamic stresses in the work material 6 to deform the work material 6 causing the work material 6 to conform with the configuration of the cavity of the die 5. A detailed discussion of the combination of static and dynamic stresses is found in Ser. No. 713,036, filed Mar. 14, 1968, now U.S. Pat. No. 3,550,417 for Process for the Hot Forming of Metals, by Robert C. McMaster, and assigned to the Ohio State University.

FIG. 2 illustrates a deep drawn hemispherical cup such as can be drawn with the present invention. FIG. 2a illustrates the punch 7a configuration and die 50 configuration used to form a hemispherical cup. Impacting of the punch 7a with vibratory-mechanical energy while simultaneously applying a low static force stretches the work material 6 and deforms it to the configuration of the die 5a in accordance with the description above.

FIG. 3 illustrates a U" bend formed using the present invention in conjunction with the punch 7b and die 51; illustrated in FIG. 3a. Impacting with vibratory-mechanical energy and applying a low static force formed this sheet metal 6 to the shape illustrated.

While FIGS. 2 and 3 show specific shapes formed by the present invention, the invention can, of course, produce shapes which require various combinations of stretching and bending to form. That is, the present invention is capable of forming complex shapes. Another major advantage in using the system and methods of the present invention resides in the fact that the static force F required to be applied to carry out the desired deformation is lower by a factor of to 100 than the force required when static force F alone is sued to deform the work material 6. Further, the present invention forms dimensionally stable configurations. There is no spI-ingback" in the shapes formed with the present invention; the shapes conform exactly to the shape of the die. No springback occurs because the work material 6 is stress relieved as it is formed due to the action of the dynamic stresses in the work material.

Another advantage of the present invention is that it facilitates the deformation of materials which are normally difficult to form. The present invention easily cold forms such difficult to form materials as titanium. The present invention reduces or eliminates breakage during the cold forming of titanium and other such materials.

Means for guiding the forming tool other than that described hereinabove may be used. More specifically, an impact coupling means supported by a plurality of diaphragms can be used in lieu of the punch 7, punch guide 4, and alignment means 3. Reference is made to copending patent application, Ser. No. 819,886, filed Apr. 28, 1969, for Intermediary lmpact Device," by Charles C. Libby and William J. White, and assigned to the Ohio State University, for a more detailed description of the intermediary impact device supported by a plurality of diaphragms. In practice, the intermediary impact device can either be the actual punch as just described or can merely be used in lieu of the alignment means 3 to transfer vibratory-mechanical energy to the punch at its mechanical resonant frequency.

Hence it is clear that while certain and specific embodiments have been illustrated and described, it is to be un derstood that modifications may be made thereto without departing from the true scope and spirit of the invention.

What is claimed is:

l. A system for the deformation of sheet material comprising: a fixed frequency piezoelectric source of vibratory electromechanical energy, a vibratory-electromechanical energy transmission line, a punch, said punch being operatively unsecured to said line through aligning means whereby said punch receives vibratory-mechanical energy by impact coupling, means for guiding said punch, a firming die, said sheet material positioned between said punch and said forming die, and means positioned at the node of said transducer for applying a static force to said transducer, said punch intermittently engaging said sheet material to combine the static stresses with the dynamic stresses created in said sheet material to form said sheet material to the shape of said punch and die.

2. A system as described in claim 1 wherein said dynamic stresses in said workpiece is further operative to stress relieve said workpiece as it is formed.

3. A system as described in claim 1 wherein said static forces applied to said transducer are on the order of 10 to times less than that required without said dynamic stresses.

41. A system as described in claim 1 wherein said system further comprises means for positioning said means for aligning between said punch and said transmission line said positioning means having, an aperture parallel to the direction of movement of said punch and an axial aperture along the longitudinal axis of said transmission line whereby said apertures retain said means for aligning in position.

5. A system as described in claim l wherein said system further comprises means for positioning :said punch in an aperture in said punch guide, said aperture being coincident with the desired direction of movement of said punch.

6. A method for the deforming of sheet material utilizing a sonic transducer and transmission line, a punch, a punch guide, and a die, the sheet work material positioned between the die and the punch guide, comprising the steps of applying static force to said transducer, said punch being operatively unsecured to said line whereby said punch receives vibratorymechanical energy by impact coupling transmitting said static force through said transmission line, and intermittently engaging said work material, combining said static stresses of said static force with the dynamic stresses of said transducer in said workpiece to form said material to the shape of said punch and die.

7. A method as described in claim 6 wherein said dynamic stresses further includes stress relieving said material as it is formed. 

1. A system for the deformation of sheet material comprising: a fixed frequency piezoelectric source of vibratory electromechanical energy, a vibratory-electromechanical energy Transmission line, a punch, said punch being operatively unsecured to said line through aligning means whereby said punch receives vibratory-mechanical energy by impact coupling, means for guiding said punch, a firming die, said sheet material positioned between said punch and said forming die, and means positioned at the node of said transducer for applying a static force to said transducer, said punch intermittently engaging said sheet material to combine the static stresses with the dynamic stresses created in said sheet material to form said sheet material to the shape of said punch and die.
 2. A system as described in claim 1 wherein said dynamic stresses in said workpiece is further operative to stress relieve said workpiece as it is formed.
 3. A system as described in claim 1 wherein said static forces applied to said transducer are on the order of 10 to 100 times less than that required without said dynamic stresses.
 4. A system as described in claim 1 wherein said system further comprises means for positioning said means for aligning between said punch and said transmission line said positioning means having, an aperture parallel to the direction of movement of said punch and an axial aperture along the longitudinal axis of said transmission line whereby said apertures retain said means for aligning in position.
 5. A system as described in claim 1 wherein said system further comprises means for positioning said punch in an aperture in said punch guide, said aperture being coincident with the desired direction of movement of said punch.
 6. A method for the deforming of sheet material utilizing a sonic transducer and transmission line, a punch, a punch guide, and a die, the sheet work material positioned between the die and the punch guide, comprising the steps of applying static force to said transducer, said punch being operatively unsecured to said line whereby said punch receives vibratory-mechanical energy by impact coupling transmitting said static force through said transmission line, and intermittently engaging said work material, combining said static stresses of said static force with the dynamic stresses of said transducer in said workpiece to form said material to the shape of said punch and die.
 7. A method as described in claim 6 wherein said dynamic stresses further includes stress relieving said material as it is formed. 